Interfacial electronic effects control the reaction selectivity of platinum catalysts

Abstract

Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

Untangling the Role of the Capping Agent in Nanocatalysis: Recent Advances and Perspectives

“…This interfacial electronic effect has been proven by Zheng et al for the selective partial hydrogenation of nitroaromatic compounds [59]. In this case, the modification of Pt catalysts with ethylenediamine (an electron-rich species) leads to an enhanced selectivity to the hydroxylamine, the product of the partial hydrogenation of the nitro group.…”

Engineering Surface Ligands of Noble Metal Nanocatalysts in Tuning the Product Selectivity

“…Very recently, Chen et al [35] reported the use of ligand-modulated electronic effect on Pt nanowires to control the hydrogenation selectivity of nitroaromatics (Figure 6c,d). The hydrogenation of nitrobenzene to aniline went through an intermediate of hydroxylaniline, known as a high-value, industrially important compound.…”

“…The anchor of surface ligands through the coordination with N, S and O atoms has been confirmed to change the intrinsic electronic states of metal by metal-ligand charge interaction. The change in electronic states of surface atoms can vary the key transition states that in turn control the product selectivity [35,[69][70][71][72], particularly for parallel reactions and consecutive reactions. For example, when Pt/Al 2 O 3 catalysts were modified by thiol-ended ligands with various lengths, all catalysts showed every similar selectivity for the hydrogenation of epoxybutene [73].…”

“…The charge density is a key to governing the binding affinity of reactants and/or transition states to active sites. The fine-tuning of surface charge density, therefore, can change the reaction pathways and may favor the formation of a specific intermediate involved in a complex reaction [35]. In this minireview, we highlight a few recent reports on how to use surface ligands on heterogeneous noble metal nanocatalysts (mainly on Au, Pd and Pt) to modulate their catalytic selectivity.…”

Understanding of the major reactions in solution synthesis of functional nanomaterials

“…Bao and co-workers [431] reported the interface between metal and oxides can be utilized to stabilize the coordinatively unsaturated ferrous sites, which could largely improve the catalytic performance towards reactions involving dioxygen activation such as CO oxidation at low temperature. Most recently, Zheng's group [432] reported the fabrication of interface between the surface capping agents and metal could impart the functionality to tune the electronic structure of the metal catalysts, which could further endow the control over the selectivity during the catalytic performance. Since the interfacial structures play a pivotal role in modulating the intrinsic properties such as catalytic behavior, considerable research efforts have been made for developing the strategy to effectively fabricate interface between metal-metal, metal-oxides, metal-semiconductor, metal-organic and so on.…”